An autotensioner used to keep constant the tension of the belt for driving the camshaft of an automobile engine is proposed in Unexamined Japanese Utility Model Publication 1-171952.
In this type of autotensioner, as shown in FIG. 6, a support shaft 32 is fixed by tightening a bolt 31 into a base 30 of the engine block. A pulley support 33 is eccentrically supported on the support shaft 32. A pulley 35 is rotatably mounted on the pulley support 33 through a rolling contact bearing 34. The pulley support 33 is provided with a cylindrical portion 36 concentrical with the support shaft 32. A bracket 37 press-fitted on the cylindrical portion 36 has an arm 38 to which a tension adjusting spring 39 is coupled in order to rock the pulley support 33 in a direction in which the pulley 35 stretches the belt.
Further, between the cylindrical portion 36 and the support shaft 32 is provided a damper mechanism 40 in the form of viscous fluid so that it will impart a rocking resistance to the pulley support 33 and prevent a high-frequency fluctuation.
In this conventional autotensioner, as shown in FIG. 7, the pulley support 33 including the cylindrical portion 36 is in the form of an eccentric cylinder having two different central axes a and b. Thus, it requires a lot of manufacturing time and cost.
A technical object of the present invention is to obviate the abovesaid problems and to simplify the manufacturing process of the pulley support of the autotensioner and to reduce the cost.